Glass cathode ray tubes employed for the presentation of color images are comprised of a glass funnel portion sealed at its wide end to a glass, dish-shaped face panel by means of a glass frit. The face panel contains on the inside surface thereof a phosphor screen which has suspended behind it a metallic shadow mask.
In the prior art it is taught that the glass of such tubes can be salvaged by immersing the seal area in an acid bath, for example nitric acid, which may be heated, to etch away a portion of the external frit area. The glass envelope is then subjected to a series of alternately hot then cold water baths which create a temperature differential between the funnel and the face panel and cause the frit seal to fracture by means of induced thermal shock.
Such techniques are known from U.S. Pat. No. 2,884,312 and U.S. Pat. No. 3,390,033.